I'm applying for their physical therapy clinical rotation at the moment, so I won't speak on that, but I can give some insight into the S&C world.
@jteitel10 already mentioned everything you need to know to maximizing your chances in this particular company. Prior experience is big time, not only on paper. When interviewing you can convey the idea that you are confident in that setting, and are familiar with it. S&C coaches are also interested in people who are willing to learn rather than set in their ways. There's a lot of different perspectives and programming in strength and conditioning. My advice is have stellar letter of recommendations, get the CSCS if possible, and volunteer or shadow S and C coaches in large volume sports. As far as getting a position, EXOS does a good job of already outlining the steps. Good luck, let us know how ti goes.
Side note, is this an internship at 1 of the 5 EXOS facilities? The other sites at corporate facilities are good and you can learn a lot about the fitness field, but the 5 main sites are a whole different beasts that are among the ranks of Cressey Performance and Sparta Science.